The study is part of the external evaluation of Mastering Maths. In summer 2015 the IPN assessed the mathematical competencies of 6.500 fifthgraders from 61 schools in NRW. The study was organised in 40 schools taking part in the Mastering Maths project and 21 other schools not involved in the project. The report is dedicated to the German Telekom Foundation which is covering the expenses of the external evaluation.